Restoration for Intensity Nonuniformities with Discontinuities in Whole-Body MRI

Signals Pub Date : 2023-10-18 DOI:10.3390/signals4040040
Stathis Hadjidemetriou, Ansgar Malich, Lorenz Damian Rossknecht, Luca Ferrarini, Ismini E. Papageorgiou
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引用次数: 0

Abstract

The reconstruction in MRI assumes a uniform radio-frequency field. However, this is violated due to coil field nonuniformity and sensitivity variations. In whole-body MRI, the nonuniformities are more complex due to the imaging with multiple coils that typically have different overall sensitivities that result in sharp sensitivity changes at the junctions between adjacent coils. These lead to images with anatomically inconsequential intensity nonuniformities that include jump discontinuities of the intensity nonuniformities at the junctions corresponding to adjacent coils. The body is also imaged with multiple contrasts that result in images with different nonuniformities. A method is presented for the joint intensity uniformity restoration of two such images to achieve intensity homogenization. The effect of the spatial intensity distortion on the auto-co-occurrence statistics of each image as well as on the joint-co-occurrence statistics of the two images is modeled in terms of Point Spread Function (PSF). The PSFs and the non-stationary deconvolution of these PSFs from the statistics offer posterior Bayesian expectation estimates of the nonuniformity with Bayesian coring. Subsequently, a piecewise smoothness constraint is imposed for nonuniformity. This uses non-isotropic smoothing of the restoration field to allow the modeling of junction discontinuities. The implementation of the restoration method is iterative and imposes stability and validity constraints of the nonuniformity estimates. The effectiveness and accuracy of the method is demonstrated extensively with whole-body MRI image pairs of thirty-one cancer patients.
全身MRI强度不均匀与不连续性的恢复
磁共振成像的重建采用均匀的射频场。然而,由于线圈场的不均匀性和灵敏度的变化,这是违反的。在全身MRI中,由于多个线圈的成像通常具有不同的总体灵敏度,导致相邻线圈之间连接处的灵敏度发生急剧变化,因此不均匀性更加复杂。这导致图像具有解剖学上无关紧要的强度不均匀,包括相邻线圈对应的连接处强度不均匀的跳跃不连续。身体也通过多重对比成像,导致图像具有不同的不均匀性。提出了一种两幅图像的强度均匀度联合恢复方法,实现了图像的强度均匀化。利用点扩散函数(PSF)对空间强度失真对每幅图像的自动共现统计量以及两幅图像的联合共现统计量的影响进行了建模。从统计数据中得到的psf和这些psf的非平稳反卷积提供了贝叶斯取心的非均匀性的后验贝叶斯期望估计。然后,对非均匀性施加分段平滑约束。这使用恢复场的非各向同性平滑来允许对结不连续进行建模。恢复方法的实现是迭代的,并且对非均匀性估计施加了稳定性和有效性约束。该方法的有效性和准确性通过31例癌症患者的全身MRI图像得到了广泛的验证。
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来源期刊
CiteScore
3.20
自引率
0.00%
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0
审稿时长
11 weeks
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